Structural Analysis of Non-Enzymatic Post-Translational Modification by Mass Spectrometry: Application to Oxidized Protein

Abstract

Proteins can be modified at the peptide backbone and the amino acid side chains, the process is so called post-translational modification. The modifications are divided into two classes of modification reaction, enzymatic reaction and non-enzymatic reaction. The typical examples of non-enzymatic modification are carbonylation, oxidation in methionine and cysteine, deamidation in aspartate and glutamate, glycation in N-terminal and amino group of lysine. Most of these modifications are irreversible and known to be implicated in cellular damage, ageing and disease. Mass spectrometry has been extensively contributing to this field of the structural characterization and quantitation. In this paper, I present identification and structural determination of oxidatively modified protein and the application to biomarker discovery, and also described the technical considerations to deal with these non-enzymatic modifications from the point of view of mass spectrometry. One of the topics is the structure determination of carbonylated protein from complex mixture obtained by the use of isotopically labeled hydrazine compound with matrix-assisted laser desorption ionization mass spectrometry. The potential protein biomarker for Parkinson's disease found by mass spectrometry is also discussed.